Originally Posted by
John E
A sudden slip of the shift lever or snap of the shift cable can throw the cage into the spokes or the chain into the gap between the low gear cog and the spokes. This is why I call low-normal a "suicide" rear derailleur.
No, though this is a common misconception.
In fact, what you describe results only if the derailleur arm is bent (as is often the case, as I described), or if it's the wrong derailleur for the freewheel. For example, if you use a 5 speed derailleur on a 4 speed freewheel, this will happen unless you add spacers in the axle to make sure it doesn't.
When setting up this type of derailleur, make sure the derailleur cage is perfectly aligned with the biggest cog when there is no cable attached. If it isn't, you have to bend the arm, or add spacers to the axle, or otherwise do something to move the whole derailleur to the right.
The best thing to do is to bend the arm, but to do that you have to completely disassemble the derailleur.
